The present invention relates to an antenna device and an electric appliance using the same.
Today, electric appliances such as personal computers are mostly provided with communication functions for connecting to commercial networks or building up a LAN. As communication formats, needs for wireless communications are rapidly increasing owing to various conveniences because cables are not needed unlike wired communications.
An example of an antenna device incorporated in a conventional personal computer is shown in FIG. 27.
In FIG. 27, a personal computer 111 comprises a main body side housing 112 accommodating a keyboard and various electric components, and a display side housing 113 including a display unit 122 for displaying visual information by electric means.
An antenna element 117 is built in a side part of the display side housing 113, and electric power of specified frequency is supplied from a current feeding unit 120 provided in the main body side housing 112 through a coaxial cable 121.
The antenna element may be also located in other positions, such as both sides or center at the upper portion of the display side housing, both sides at the lower portion of the display unit, or both sides of the keyboard in the main body side housing.
Herein, the personal computer 111 is provided with an electromagnetic shield 123 in the display unit 122 or back side of the display side housing 113 in order to shield undesired radiation from the internal electric circuits. In the wide screen trend of the display unit 122, the majority of the space of one side of the display side housing 113 is occupied by the display unit 122.
Therefore, the radio wave from the antenna element 117 incorporated in the display side housing 113 is radiated, as shown in FIG. 28, from the region partially free from the electromagnetic shield 123 at the back side of housing 113. Accordingly, the radiation directivity of the antenna element 117 is unidirectional having an intensity in one direction only.
In a wireless LAN composed by computers, generally, the radiation partners of communication is not fixed in one direction only, and the radiation characteristic of the antenna element is preferred to be uniform as far as possible, that is, omnidirectional.
In the prior art, however, the incorporated antenna element is unidirectional, and communication troubles often occur and comfortable environments of use may not be offered.